The invention relates to a rod lens array, an LED print head that includes the rod lens array, an image forming apparatus that includes the LED print head, a contact image sensor head that includes the rod lens array, and an image reading apparatus that includes the contact image sensor head.
In general, a rod lens array may be used in applications such as, but not limited to, a light-emitting diode (LED) print head and a contact image sensor. The LED print head may be used for an exposure unit of an LED printer, whereas the contact image sensor may be used for a reading unit of an image scanner. The rod lens array has a plurality of gradient index lenses (referred to as “lenses” hereinafter) that are arrayed in line, and may have an example configuration in which the plurality of lenses are arrayed in parallel to each other between two substrates, or two side plates, that are fixed with use of an adhesive or any other suitable fixing method. The two substrates each may be a plate member made of a material such as, but not limited to, a phenol resin, an acrylonitrile butadiene styrene (ABS) resin, an epoxy resin, and an acrylic resin. For example, reference is made to Japanese Unexamined Patent Application Publication No. 2005-181949.